Bar codes have found increasing numbers of uses in recent years in connection with machine sensing of documents, containers, railway cars, etc. A bar code is relatively simple to sense, and enables the storage of a substantial amount of information in a relatively small area.
One use for bar coding which has been proposed, and which appears to have a number of important advantages, is in association with bank checks to provide a check or document identification number (DIN) which can be imprinted upon a check or other document as it enters a financial institution for processing, and can be subsequently sensed from the check and used in document sorting and other processing. A number of methods have been proposed for printing of such bar code information, including ink jet printing. One representative document handling system employing ink jet printing means for printing of bar codes on documents is shown in U.S. Pat. No. 3,988,571, issued on Oct. 26, 1976.
Bar codes may be printed by mechanical impact-type printers, as well as ink jet printers. One type of mechanical bar code printer, employed in printing a color bar code, consisting of bars of different colors in accordance with a predetermined code, is shown in U.S. Pat. No. 3,738,263, issued on June 12, 1973, and assigned to the assignee of the present Application. Another type of color bar code printer is disclosed in Canadian Pat. No. 1,013,615, issued July 12, 1977, and also assigned to the assignee of the present Application.